<!doctype html>
<head>
  <meta charset=utf-8>
  <title>Baseline fullscreen reference</title>
  <style>
    div {
      position: fixed; top: 0; left: 0;
      height: 100%; width: 100%;
      background: green;
    }
  </style>
</head>
<body>
  <div>0</div>
</body>
